Camshaft phasers are used in modern internal combustion engines for variably adjusting the valve timing of gas-exchange valves in order to allow the phase relationship between the crankshaft and the camshaft to be variably adjusted within a defined angular range between a fully advanced position and a fully retarded position. For this purpose, camshaft phasers are integrated into a drive train which serves to transmit torque from the crankshaft to the camshaft. This drive train may be implemented, for example, as a belt drive, chain drive or gear drive.
German Patent Document DE 10 2008 051 755 A1 discloses a vane-type camshaft phaser having a rotor, a stator, a driving wheel, a locking mechanism, and a spring. The stator is non-rotatably connected to the driving wheel. The locking mechanism couples and decouples the stator and the rotor, which are rotatable relative to one another, by engaging in a recess in the driving wheel. Moreover, the rotor and the driving wheel are provided with set screws to hold the spring. Relative rotation causes the spring to exert a torque in a direction opposite to the direction of relative rotation. The spring is in the form of a spiral spring which has radially extending coils and is disposed on the side facing away from the camshaft. The spring cavity surrounding the spring is bounded by a spring cover to counteract axial displacement of the spring. This ensures that the spring ends remain in position at the set screws, preventing them from slipping axially off the set screws due to the vibrations occurring during engine operation and thus from causing damage in the internal combustion engine. Because of resonance, the vibrations may cause spring coils to contact the surrounding boundaries of the spring cavity and be damaged by impulsive excitation.